Embodiments of the present technique relate generally to diagnostic imaging, and more particularly to a technique for adaptive configuration of a source and a detector in an imaging system for optimal data acquisition.
Radiographic imaging systems typically include a radiation source that emits radiation towards an object, such as a patient or a piece of luggage. A radiation beam, after being attenuated by the object, impinges upon an array of radiation detectors. Generally, the radiation beam intensity received at the detector array depends upon the attenuation of the radiation beam through the scanned object. Particularly, each detector in the detector array generates a separate signal indicative of the attenuated beam received by the detector. Subsequently, each detector transmits the generated signal to a data processing system for analysis and further processing to facilitate image reconstruction.
Conventionally, radiation detectors are employed in emission imaging systems, for example, nuclear medicine (NM) gamma cameras, computed tomography (CT) systems and positron emission tomography (PET) systems. Typically, the CT systems include an X-ray source and a detector array that are rotated about a gantry encompassing an imaging volume around the object. Particularly, the detector array in the CT systems employs detectors that convert X-ray photon energy into current signals that are integrated over a time period, then measured, and ultimately digitized. Furthermore, the CT imaging systems typically include photon-counting (PC) detectors that provide dose efficient X-ray spectral information, energy discrimination and material decomposition capabilities. Conventional PC detectors, however, are subject to saturation effects at high X-ray flux, for example, at or above 5-100 million counts per sec per millimeter squared (Mcps), due to pile-up and polarization. Detector saturation causes loss of imaging information, thereby resulting in severe artifacts in reconstructed X-ray projection and CT images. Some CT systems, therefore, employ energy integrating (EI) detectors that do not experience saturation at high X-ray flux rates. These EI detectors, however, provide only limited energy information. Additionally, at low flux rates, these EI detectors suffer from electronic noise.
Accordingly, recent detectors have been designed to provide either or both of photon counting and energy discriminating feedback. These types of detectors, however, still have limited count rates. Moreover, these detectors may not cover broad dynamic ranges encompassing very high X-ray photon flux rates typically encountered with conventional CT systems, where the very high X-ray photon flux rates ultimately lead to detector saturation.
Several techniques have been proposed to address detector saturation. These techniques include simultaneous readout of PC and EI data so that EI data is always available in regions where the PC data is saturated and PC data is available in regions where the flux is small. Although these simultaneous readouts solve the problem of saturated regions by providing EI data, these techniques fail to provide energy information in the saturated regions. Accordingly, alternative techniques have been designed to employ a predictive algorithm for configuring a desired detector setting for acquiring imaging data in different regions. It is however noted that actuation of the predictive algorithm may be regional on the detector making it difficult to select a setting (PC or EI) that works for neighboring regions.
A particularly challenging task is to configure detector settings for imaging coronary vessels in a lung field. As the lung field is adjacent to the coronary vessels and the sternum, high flux and low flux regions are proximally positioned and are encountered at the detector in rapid succession in time. Accordingly, switching a detector from a PC mode to an EI mode in conventional imaging systems may not be fast enough to allow acquisition of sufficient data for an efficient image reconstruction which, in turn, may affect accuracy of a diagnosis.
It would therefore be desirable to design a method and a system that overcome flux rate limitations of conventional detectors and organize acquisition of sufficient data for different system configurations to reconstruct a high quality image. Additionally, there is a need for a system that provides faster scanning and efficient material discrimination capability even with lower doses of radiation.